am49bds640ah Meet Spansion Inc., am49bds640ah Datasheet - Page 37

• Manufacturer Part Number: am49bds640ah
• Description: Stacked Multichip Package Mcp , Flash Memory And Psram Cmos 1.8 Volt-only Simultaneous Read/write, Burst Mode 64 Megabit 4m ? 16-bit Flash Memory, And 16 Mbit 1m ? 16-bit Psram
• Manufacturer: Meet Spansion Inc.

out margin, the erase command should be reissued to
improve the program margin.
It is the responsibility of the user to preprogram all
PPBs prior to issuing the All PPB Erase command. If
the user attempts to erase a cleared PPB, over-era-
sure may occur making it difficult to program the PPB
at a later time. Also note that the total number of PPB
program/erase cycles is limited to 100 cycles. Cycling
the PPBs beyond 100 cycles is not guaranteed.
DYB Write Command
The DYB Write command is used for setting the DYB,
which is a volatile bit that is cleared at hardware reset.
There is one DYB per sector. If the PPB is set, the sec-
tor is protected regardless of the value of the DYB. If
the PPB is cleared, setting the DYB to a 1 protects the
sector from programs or erases. Since this is a volatile
December 5, 2003
A D V A N C E
Am49BDS640AH
I N F O R M A T I O N
bit, removing power or resetting the device will clear
the DYBs.
PPB Status Command
The programming of the PPB for a given sector can be
verified by writing a PPB status verify command to the
device.
PPB Lock Bit Status Command
The programming of the PPB Lock Bit for a given sec-
tor can be verified by writing a PPB Lock Bit status ver-
ify command to the device.
DYB Status Command
The programming of the DYB for a given sector can be
verified by writing a DYB Status command to the de-
vice.
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